1. Field of the Invention
This invention relates to independent suspension systems for vehicles.
2. Description of the Related Art
Independent suspension systems for vehicles frequently employ one or two control arms (also referred to as wishbones or A-arms) to locate a wheel hub carrier or steering knuckle with respect to the vehicle chassis and to allow movement of the wheel in a generally vertical direction. A spring, that can be virtually any type of spring such as a coil spring or a pneumatic spring, opposes the upward movement of the wheel. The inboard end of each control arm is connected to the vehicle body by an articulated bearing or joint, while the outboard end is connected in each case to the wheel hub carrier by a second articulated bearing or joint so as to form a four bar linkage. Frequently, the spring is of an axial type such as a coil spring or a hydropneumatic strut, such that the spring deflection is along the same axis as the spring force, and has its upper end connected to the vehicle body, while its lower end is connected to one of the two control arms. To allow the wheel to steer, the articulated joint at the outboard end of each control arm can be a ball-joint. Alternative suspension arrangements, such as the well known McPhearson strut suspension, use a single suspension control arm.
In automobile applications, loads and ball joint articulation can be accommodated relatively easily. However, In heavy duty, high mobility truck applications, suspension articulations and suspension loads can be extreme (up to 500 mm and 6 tonnes static with a 5 g dynamic component). In such situations, accommodation of suitably sized ball joints with adequate articulation and load bearing capacity presents a severe challenge. Traditionally, ball joints have been mounted directly on the control arms or the stub axle, and a suitable seal arrangement provided. Such arrangements cause difficulties in fitting, servicing and inhibit angulations. Alternatively, the seal may be self-contained on the ball joint. This arrangement results in very large bore requirement for fitting into the stub axle or control arm and inhibits articulation.
In the prior art European Patent Specification No. 0832769 discloses a stabiliser link rod with integral sockets at each end, each of which houses a ball stud. In U.S. Pat. No. 6,287,040 there is disclosed a ball and socket joint in which the ball pin is shaped to co-operate with a sealing boot to prevent ingress of dirt. A further type of ball joint is described in U.S. Pat. No. 5,772,352 which has a pair of spaced-apart bearing sheets for supporting a ball within a socket. With use and wear the bearing sheets will come together and further wear results in play in the ball joint giving an indication of wear and prompting replacement. In U.S. Pat. No. 6,758,986 there is disclosed a device for securing a bearing shell. In a housing of a ball joint. U.S. Pat. No. 4,111,571 discloses a ball and socket joint with means for detecting wear in the joint. In all of the aforementioned patent specifications me housing for the ball pin is integral with a link element such as a steering control arm, stabiliser, link rod, knuckle or the like.
According to the invention, there is provided an independent suspension system, including:
at least one control arm,
the or each control arm having an inner end and an outer end,
the inner end for connection by means of a first articulating joint to a vehicle body and the outer end for connection to a wheel hub by means of a second articulating joint for mounting the wheel hub on the vehicle body,
spring means for mounting between the control arm or one of the control arms and the vehicle body,
the second articulating joint comprising a ball joint having a ball pin rotatably mounted in a complementary ball housing, the ball pin having a spherical ball head with a shank extending outwardly therefrom, the ball head being rotatably mounted and sealed within the complementary ball housing with the ball pin shank projecting outwardly from the ball housing,
said ball housing having an opening through which the ball pin projects, a seal being mounted between the ball pin shank and the ball housing to seal said opening,
first connector means for releasably engaging an outer free end of the shank with one of the control arm and the wheel hub and second connector means for releasably engaging the ball housing with the other of the control arm and the wheel hub.
Advantageously each ball joint at an outer end of the control arm or arms is a separate unit which is demountable from the control arm and the wheel hub and can be installed without dismantling the ball joint. Thus there is no possibility for dirt and other foreign matter to get into the ball joint when fitting the ball joint. Also the fitting of the ball joint is simplified as it is only a matter of attaching the two connectors between the ball joint and the control arm and wheel hub.
In one embodiment of the invention connector means is provided for engagement of a control arm with the ball joint in a manner which allows adjustment of the effective length of the control arm.
In another embodiment the control arm and the ball joint are releasably interengagable by means of a two-part threaded connector having a first part comprising a threaded bore and a second part comprising a threaded shank for complementary threaded engagement within the bore, one part being on the control arm and the other part being on the ball joint.
In a further embodiment the threaded bore is provided in the control arm and the threaded shank is provided on the ball joint. The threaded shank may be provided on the ball housing extending outwardly therefrom.
In another embodiment the threaded bore is provided on the ball joint and the threaded shank is provided on the control arm.
In a preferred embodiment, two control arms are provided, namely, an upper control arm and a lower control arm for mounting between the vehicle body and the wheel hub to support the wheel hub on the vehicle body.
In another embodiment, the control arm has a threaded bore adjacent ant outer end of the control arm for reception of a complementary threaded shank which projects outwardly of the housing. Thus, the ball joint can be screwed onto the end of the control arm and this conveniently allows length adjustment of the control arm.
In an alternative arrangement, the control arm has a threaded shank adjacent an outer end of the control arm for engaging with a complementary threaded bore in the housing.
In a further embodiment, the control arm and/or the wheel hub has a through hole for reception of the shank of the ball joint which is engagable within the hole with an outer threaded end of the shank projecting therethrough and being secured on the control arm or hub by a locknut.
Preferably, an intermediate portion of the shank is tapered and a bore of the through hole is tapered for mating engagement with the tapered shank portion.
In another embodiment the ball housing has a socket for reception of the ball pin, the socket having an inner end and an outer end, an annular stop being provided at the inner end of the socket, said annular step defining the opening in the ball housing through which the ball pin projects, a bearing mounted within the socket for rotatably supporting the ball head within the socket, the outer end of the socket having a threaded outer bore portion, a retaining nut being engagable within the complementary threaded outer bore portion of the socket to secure the bearing within the socket, the retaining nut engaging an outer end of the bearing to clamp the bearing between the retaining nut and the annular step at the inner end of the socket.
In another aspect the invention provides a modular ball joint assembly, including:
a ball pin rotatably mounted in a complementary ball housing,
the ball pin having a spherical ball head with a shank extending outwardly therefrom,
the ball head being rotatably mounted and sealed within the complementary ball housing with the ball pin shank projecting outwardly from the ball housing,
said ball housing having an opening through which the ball pin projects,
a seal being mounted between the ball pin shank and the ball pin housing to seal said opening,
the ball housing having a socket for reception of the ball pin,
the socket having an inner end and an outer end,
an annular step being provided at the inner end of the socket,
said annular step defining the opening in the ball housing through which the ball pin projects,
a bearing mounted within the socket for rotatably supporting the ball head within the socket,
the outer end of the socket having a threaded outer bore portion,
a retaining nut being engagable within the complementary threaded outer bore portion of the socket to secure the bearing within the socket,
the retaining nut engaging an outer end of the bearing to clamp the bearing between the retaining nut and the annular step at the inner end of the socket,
a threaded connector shank projecting laterally outwardly from a side of the ball housing.